Rational Design of a Hydrophilic Perovskite Ultraviolet Photocatalyst for Mediating a Sensitive and Controllable Nucleic Acid Assay

CsPbX 3 perovskites are emerging photocatalysts with promising biosensing applications, yet designing highly active ultraviolet photocatalysts and clarifying their photocatalytic mechanism in the aqueous phase remain challenging. This study reveals the oxidase-like activity of hydrophilic CsPbX 3 nanoparticles (NPs) under ultraviolet light (UV-OXD-like activity), wherein soluble oxygen is catalyzed into singlet oxygen ( 1 O 2 ), leading to rapid oxidation of the chromogenic substrate within seconds. Halogen atoms and doped metal ions can significantly influence the band structure of the CsPbX 3 NPs. Among these, Cl atoms endow a wide bandgap (∼3.0 eV) favorable for UV absorption of CsPbX 3 NPs, while the deep trap states introduced by Bi 3+ promote nonradiative recombination, thus enabling Bi 3+:CsPbCl 3 NPs to have excellent UV-OXD-like activity. Notably, ascorbic acid (AA) formed by alkaline phosphatase (ALP)-catalyzed hydrolysis of the substrate can passivate deep trap states through hydrogen bonding. The presence of the target nucleic acid activates the trans-cleavage activity of LbCas12a, releasing ALP from magnetic beads. Accordingly, an enzyme cascade reaction coupled with a UV-controlled readout is proposed for the BRAF V600E assay with a low limit of detection (0.10 pM, preamplification-free) and applied to human thyroid cancer tissue samples. This work provides a perspective for the design and bioapplication of hydrophilic perovskite-based UV photocatalysts.